 |
Daylight Saving Time changes effect on CICS Transaction Server
|
| | | Abstract | | For many countries Daylight Saving Time (DST) changes the last Sunday in October or the first Sunday in November. You would like to understand the impact that the DST time change has on CICS Transaction Server. You would also like to know when DST will begin and end in your country, and the action that you will need to take. | | | | | | Content | Beginning in 2007, most of the United States, Canada, Bermuda, and Bahamas begins DST at 2:00 a.m. on the second Sunday in March and reverts to standard time on the first Sunday in November. In the U.S., each time zone switches at a different time.
In the European Union (EU), Summer Time begins and ends at 1:00 a.m. Universal Time (Greenwich Mean Time). It begins the last Sunday in March and ends the last Sunday in October. In the EU, all time zones change at the same moment.
» See more information about elsewhere in the world.
| What will happen if you fail to update your systems? | Systems or applications that rely on date or time processing functions could make incorrect calculations. Calendar, scheduling, or synchronizing problems could arise where systems use date or time stamps, or if dates or times are processed or manipulated in any way.
In short, if your system makes date or time calculations, you might experience calculation errors.
See Effect of daylight saving time changes in the CICS information center for more details. The section on Time stamping log and journal records explains why a local time change, forwards or backwards, has no effect on CICS logging or journaling, or on CICS restarts, but could affect the operation of utility programs such as DFHJUP. If using user or vendor written journal utilities or DFHJUP with SUBSYS, when adjusting clocks backwards, it says you might need to stop CICS regions until the new local time passes the old time at which the change was made.
| How do you update CICS to reflect the DST time change? | If you change the MVS system time-of-day at any other time than midnight and you have a CICS region running, then you should immediately enter a CEMT PERFORM RESET (or EXEC CICS RESETTIME) command to synchronize the CICS time-of-day with the system time-of-day. You should not wait until midnight to synchronize the CICS and system time-of-day. If CICS is down when you change the system time-of-day then the CICS time-of-day will be reset automatically when you bring CICS back up.
If you set the CICS system initialization parameter AUTORESETTIME to YES, CICS automatically issues a PERFORM RESET command to synchronize the CICS time-of-day with the system time-of-day at the next local midnight. That is, if the CICS time-of-day differs from the system time-of-day by more than 30 minutes. So, if you reset the MVS system time just before midnight then you will not have to enter CEMT PERFORM RESET in your CICS regions.
If you set the CICS system initialization parameter AUTORESETTIME to NO or let it default to NO, CICS does not automatically update the CICS time-of-day. CICS issues message DFHAP1500 to indicate that a CEMT PERFORM RESET command is required to synchronize the CICS time-of-day with the system time-of-day.
The system time-of-day and CICS time-of-day need to be synchronized on your CICSPlex SM CMAS and WUI server address spaces as well. Failure to do so could result in symptoms such as abend AICG or BATCHREP commands receiving timeout.
To verify if CICS is using the correct time, you can look at the SYSLOG. If the time stamps of the MVS messages do not coincide with the time stamps of the CICS messages, then they are out of sync. Another option could be to check the DFHIC0801 message created at midnight. A DFHIC0801 message is created anytime the CICS local date and time is altered, such as: - at midnight when the MVS system time-of-day is reset to zero
- at PERFORM RESET or recycle time when CICS local time-of-day and MVS system time-of-day are synchronized
CICS Transaction Server for VSE/ESA V2.3 and V1.1.1 do not support the AUTORESETTIME system initialization parameter or issue message DFHAP1500. Therefore, a manual reset is required. Either restart your CICS region or enter a CEMT PERFORM RESET command to allow the CICS and system clocks to synchronize. | | | | | | | | Product Alias/Synonym | | CICS/VSE CICS VSE CICS/TS CICS TS CICS Transaction Server | | |
| | |
|
|
| IBM, the IBM logo and ibm.com are trademarks of International Business Machines Corp., registered in many jurisdictions worldwide. Other product and service names might be trademarks of IBM or other companies. A current list of IBM trademarks is available on the Web at "Copyright and trademark information" at www.ibm.com/legal/copytrade.shtml. |
|
|
|
|
| Please take a moment to complete this form to help us better serve you. |
|
 |
|
|
|
|
|
|
| Product categories: |
|
| | Software | |
| | Host Transaction Processing | |
| | Transaction Servers | |
| | CICS Transaction Server | |
| | Availability | |
|
| Operating system(s): |
| |
z/OS, z/VSE
|
|
| Software version: |
| |
1.1.1, 2.3, 3.1, 3.2, 4.1
|
|
| Reference #: |
| |
1220678
|
|
| IBM Group: |
| | Software Group |
|
| Modified date: |
| | 2009-10-23 |
|
|
